Ignition system for internal



Oct. 7, 1952 MACKAY 2,612,887

IGNITION SYSTEM FOR INTERNALCOMBUSTION AND LIKE ENGINES Filed Aug. 18,1949 3 Sheets-Sheet l E. G. MACKAY Oct. 7, 1952 IGNITION SYSTEM FORINTERNAL-COMBUSTION AND LIKE ENGINES Filed Aug. 18. 1949 3 Sheets-Sheet3 hum/70,?

5 A k/6 fl/Aam/ Patented Oct. 7, 1952 IGNITION SYSTEM FOR INTERNAL-COMBUSTION AND LIKE ENGINES.

Eric Glen-Mackay, Hawthorn, Victoria, Australia ApplicationAugust 1s,1949, 'SerialLNo. 111,036 In Australia September 17,1948

This invention relates to ignition systems for internal combustionengines and particularly magneto ignition systems for multi-cylinderinternal combustion and like engines;

With the continued increase in the number of cylinders employed inaircraft engines, the problemofproviding efiicient ignition therefor hasbecome increasingly difiicult. For example a 28 cylinder engine runningat approximately 3,000 R. P. M. would require a total of approximately42,000 ignition sparks per minute from a 28 point magneto: Known typesof magnetos are not able toprovi'de such a high output and consequentlyit has previously been necessary to employ two 14 point magnetos'inorder to obtain the desired total output. As it is customary'for safetypurposes, to provide aircraft engineswith dual ignition. systems; itfollows thatitisnecessary to fit four such. magnetos toeach engine inorder to obtainthe desired performance.

.Itsis well recognised thatknown types of magnetos' arenormally limited.tov a maximum output of approximately 301100.. ignition sparks perminutes. .At this: figure. however. efli'ciency is relatively low andconsequently it. is usually con! sidered essential. to limit. theoutput. to. approximately 25,000 ignition sparks per minute;- for. sat.-isfactoryperiormance- The factor which prevents ahigher eiiicient outputisnot electrical or. magnetic but mechanical. When the outputot themagneto. approaches 30,000 ignition sparks per minute the usual. singlesetof. cam operable and spring influenced contacts: commonly knownas;breaker points, employed. for making-and breaking the primary coilcircuit, rapidly lose efficiency in that they are not 13 Claims. (Cl.I2'3--148') A further object is to provide an improved battery ignitionsystem incorporating cam operable relatively reciprocatory contacts andwhich is oapableof a materially increased output if desired at aslowercam speed than hitherto.

If desired the improved magneto ignition system may incorporate abooster battery soas to provide an adequate supplyof current for bothstarting as well asat high engine speed without having to out off; thebattery current whilst in addition the. effective output of the; magnetois materially increased; without; any increase or its normal breakerspeed.

Other objects and various novel constructional features of the inventionwill be more. readily apparent from the following description. of.several practical embodiments.

Referring to the drawings. which form part'of this specification:

allowed sufilcient time to close, due inter to the inertial-of. themovable: parts. thereof.

The primary object of the present invention is to provide. an improved.ignition system. for multl cyl'inde'r internal. combustion. and. likeen.- gines which. materially increases the efiective output of eachmagneto in, accordance with requirements without increasingitsnormal.breaker speed. For example,;. in accordance with. the present invention,the effective. output of each magneto operating within the same breaker.speed range as. hitherto, may be raisedto the order of about 50,000 to100,000or more ignition impulses or sparks per. minutewhich thusenables. a single magneto to easily meet the requirements. for. ex.-ample, of a 28 cylinder engine operating. at approximately 3,0001R. P.M;

Another object. is to provide an improved mag.- neto. for the purposeindicatedfiwhi'ch has a much greater efiective output than hitherto.

Figure 1 is a diagrammaticview of an ignition system incorporating fourpairs of relativelyv reciprocatory contacts operablebyacommon cam and a.rotatable contact" selector in accordance with one embodimentof thepresent invention.

Figure. 2 is a part sectional, side elevationv of an improved magnetofor incorporation. in. the new ignition system.. I

Figure 3 is a wiring diagram of an ignition system in accordance. withamodification. which involves theiuse of. four pairs. of relativelyreciprocatory contacts operable by two multi-lobe cams.

Figure 4 is a Wiring diagram. of a. magneto ignition system inaccordance. with. a further embodiment which includes th use of'an oddnumber of pairs of' relatively reciprocatory contacts and a commutatorhaving a greater number of segments.

Figure 5 is a: semi-diagrammatic, perspective view of-part ofa magnetoshowing one suitable arrangement for operatively connecting the pairs ofcontactsand the commutatorseen in Figured.

Figure 6* is aside elevation, on a reduced scale. of a still furtherembodiment in which the mag..- neto and the plurality of pairsof'reciprocatory, contacts and commutator associated therewith areconstructed as separate units so that they may be located. remote fromeach other. inac-- ing of the magneto induction coil to facilitateengine starting.

Figure 9 is a modification of the ignition system seen in Figure 8 andin which the primary winding of the induction coil consists of a pair ofseparate coils.

Figure is a diagrammatic view of a still furthermodification of Figure8.

According to the several embodiments illustrated in the drawings, theimproved ignition system includes an induction coil having at least aprimary or low tension winding which is common to a plurality ofcircuits, a plurality of pairs of circuit breaker contacts which arerelatively reciprocatory and mechanically operable with each pair ofcontacts included in at least one of said circuits, separate circuitmaker means which are also common to said circuits for completing eachof them in sequence to the exclusion of all others, and means forsynchronizing the movements of said pairs of circuit breaker contactsand said circuit make means whereby agreater output of electricalimpulses is obtainable than would be possible if the ignition sytemincluded a single pair of contacts only for both making and breaking theprimary circuit. This desirable result is obtained without reducing theminimum time required forensuring effective closing of each of theplurality of pairs of contacts. In this regard it is generallyrecognized that the maximum speed at whicha pair of such contacts iscapable of operating efficiently is of the order of 25,000 openingmovements per minute.

Any suitable type of either high or low tension magneto may be employedin that the ignition system may be readily adapted to include a magnetoof the rotating armature, polar inductor or rotating magnet types.Alternatively, a magneto of the type employing electro magnets insteadof the conventional permanent magnets may be adopted if so desired.

The aforesaid circuit maker means preferably consists of a commutator orlike rotary switch device which is particularly suitable for high speedoperation. The segments of such a commutator preferably correspond innumber with the magnetic poles of the magneto in which case the brush ofthe commutator and magneto rotor shaft are operatively connectedtogether so as to rotate at the same speed and thus enable the segmentsto periodically change the pairs of contacts as hereinafter described.

'In some instances the number of the commutator segments may alsocorrespond with the number of pairs of contacts employed and a commonsingle lobe cam may be provided for actuating these contacts. The latterarrangement is however not essential and may be varied. Inthe embodimentillustrated in Figure 1, four pairs of contacts 2 are arranged incircumferentially spaced relationship around a common rotatable cam 3 sothat the pairs of contacts are opened by the cam in rotation, one of thecontacts of each pair being spring influenced as at 4 so as normally tomaintain each pair of contacts closed. i In this case four commutatorsegments 6 are provided so as to correspond with the number of pairs ofcontacts employed. Consequently the cam 3 and the commutator brush 1rotate at the same speed and therefore may be carried by the magneto orany other common shaft 8 although for convenience of illustration it hasbeen desirable to show the cam and the brush on separate Shafts.Assuming that the maximum speed-for 4 eifective operation of each set ofpoints would be limited to approximately 25,000 breaks per minute, itwill be appreciated that in this case the output from the single magneto9 would be approximately 100,000 impulses per minute. Furthermore as thefour pairs of contacts and the commutator segments have been wired inseries with the low tension winding H of the magneto and a single lobecam is employed, it will be apparent that each pair of contacts 2 isopen during a relatively short movement of the lobe tip such for exampleas 20 in which case 340 of cam movement are provided for the contacts toclose.

The length of each commutator segment 6 is such that each pair ofcontacts has adequate time to open whilst the brush is traversing itsrespective segment. Normally the brush is adapted to make and each pairof contacts is adapted to break the circuit although it will beappreciated that at very high speed the brush may have commenced totraverse each segment before the respective contacts have actuallyclosed in which case the contacts are adapted to both make and break thecircuit.

Experience has shown however that if the cam and commutator brush areadapted to operate at the same speed and a single lobe cam is employed,undesirable hammer or bounce is likely to develop in the opening andclosing movements of the contacts at highspeed. In order to avoid thisobjection, the commutator brush and the cam are preferably mounted onseparate shafts which are geared or otherwise operatively connected sothat their speed may be synchronised in accordance with requirements.This also enables a multilobe cam to be employed.

A suitable arrangement is illustrated in Figure 2 where the commutatorand the plurality of contacts and the parts associated therewith areembodied in any suitable type of magneto so. as to form a single unit.For example, the commutator brush 1 may be spring influenced as at 12and carried by an axial extension l3 of the magneto shaft l4 with thesegments arranged in circumferentially spaced relationship around theshaft extension. The cam may be carried by a suitable lay shaft [6 withthe pairs of contacts 2 arranged in circumferentially spacedrelationship around the cam. The lay shaft and magneto shaft extensionmay be operatively connected together by any suitable reduction gearingI1. Instead of using a common cam to operate all of the pairs ofcontacts, two or more cams 311 may be providedand arranged inlongitudinally spaced relationship on their shaft with their lobes l8out of registry. I

The latter type of arrangement is illustrated diagrammatically in Figure3 of the drawings although it will be appreciated that the cams havebeen shown as mounted on separate shafts for convenience ofillustration. In this case four pairs of contacts 2 and a commutatorhaving four segments 6 are employed, the contacts being arranged in twoassemblies, each of which has its own multi lobe cam. If four lobe camsare employed, the brush and cam shafts l3, l6 are connected together byfour to one reduction gearing. It will be appreciated that by employingreduction gearing as aforesaid the cam speed is materially reduced andundesirable hammer and bounce as aforesaid is eliminated.

If desired provision may be made for periodically reversing the polarityof the aforesaid contacts. As seen in the embodiment shown in Figures 4and 5 this may be achieved by employins-an oddv number of pairs of"contacts and. a cornutator which has a greater number of se ments and isadapted to rotate at a relatively higher speed. The number of segmentsemployed constitute a multiple of the number of contacts. In theembodiment illustrated, three circumferentially spaced pairs of contacts2 are provided and the commutator has siX segments, the contact cam 3abeing mounted on a separate shaft l6 which is geared to the brush shaftby two to one reduction gearin l 1. As seen in Figure 5, the brush isalso carried by the rotary magneto shaft I 4 and the arrangement is suchthat the polarity of the contacts is changed at each successive openingmovement and thus effectively prevents the undesirable transfer of metaltherebetween.

The invention is not limited to ignition systems in which a new type ofmagneto as illustrated in Figure 2 is employed. Obviously existing typesof magnetos 9 may be incorporated in the system and in this case thecommutator and the plurality of contacts and parts associated therewithmay be formed as a separate unit. As illustrated in Figure-6, the lastmentioned parts may be housed in a separate casing 2| connected byflexible or any other suitable leads 22 with the primary winding of themagneto so that the separate casing may be remotely located in relationto the magneto if found necessary.

Another embodiment is shown in Figure 7 wherein the system includes amagneto 9a of the type in which electro magnets are employed instead ofthe usual permanent magnets. For example, the rotary magnets or inductorbars 23 may be energised by a battery 24 through appropriate slip rings.The circuit in this case includes a commutator having six segments 6whilst a three lobe cam 311 may be employed for actuating two pairs ofcontacts 2. In this case, as the magneto shaft, cam and brush all rotateat the magneto consists of two sections whicharewired same speed, thecam and the brush may be con,-

veniently mounted on the magneto shaft. I

It will be appreciated from the foregoing that those embodiments of theinvention illustrated in Figures 1 to 7 are equally applicable to eithermagnetoor battery ignition systems. In either case a materiallyincreased output is obtainable if desired at a slower cam speed thanthat normally required for use in similar ignition systems but in whicha single pair of contacts only is employed. v

Although the invention has been described and illustrated asincorporating a pluralityof independent pairs of reciprocatory contactsas aforesaid, it will be appreciated that the p irs of contacts may beelectricallyconnected in tandem or in any suitable manner if so desiredin order to reduce the weight of the contact breaker arms and the springpressure thereon.

In accordance with a modification as illustrated in Figures 8, 9 and 10provision is made for including both a magneto'e and a battery 26in thecircuit in order to ensure an effective supply of current for startingpurposes as well as when the engine is running at high speed withouthaving to cut off the supply of battery current. For

this purpose, it is: essential to alternately reverse the: flow of theunidirectional battery current through the primary winding II in orderthat it may match the alternating current of the magneto therethrough.An arrangement for this purpose is described and illustrated in mycopending Australian patent appliuation, No.

22,258/48 in which the primary winding" of the in circuit with abattery. As. seen in E-igure.8,.the primary winding may consist of asingle coil provided with a substantially central tap 21 connected to acommon lead 28. from the battery .circuit so as to electrically dividethe primary Winding into two sections.

Alternatively the primary winding may consist of two separate andsubstantially identical coils 29, 3| as illustrated in Figure 9. In thiscase the coils are preferably Wound in longitudinally spacedrelationship upon a common core so as to ensure substantial matching ofthe coils and thus minimize undesirable interference therebetween.

In both of the embodiments illustrated in Figures 8 and 9, the batterycircuit includes a plurality of pairs of contacts 2 and an associatedcommutator 32 as aforesaid. In this case however the commutator inaddition to serving as the contact circuit maker also performs theadditional function of serving as circuit changing means for alternatelyincluding the said sections in the battery circuit in such a manner thatthe battery current flows first in one direction in one of the sectionsand thence inthe opposite direc-- tion in the other section to therebyalternately reverse the battery current flux in the induction coil tomatch the alternating magneto flux there- In the embodiments illustratedin Figure 8, the commutator is adapted to change the battery circuit tothe primary coil through the pre-selected contacts Whilst in themodification shown in Figure 9 the commutator functions to change thebreaker circuit through the pro-selected separate primary coils.

It is generally recognised that normal types of battery ignition systemsare limited to an output of approximately 18,000 impulses per minute.Also that conventional types of magneto ignition systems are limited toan output of approximately 28,000 impulses per minute. By way ofcomparison the outputof the ignition system above described withreference to Figures '7, 8 or 9 is capable of an efficient output ofapproximately 48,000 to 50,000 impulses per mintue. Such a performancewould adequately meet the requirements of a multi cylinder internalcombustion engine of the type used in high speed automobiles.

In the embodiments illustrated in. Figures 8 and 9 the eight polemagneto rotor may be adapted to rotate at the same speed asboth thecommutator and the cam for actuating the pairs of contacts. In this casethe system'would be capable of meeting the requirements. of a fourstroke eight cylinder engine operating at 12,000 R. P. M. which wouldnecessitate theprovision of 48,000 impulses per minute ata magneto rotorspeed of 6000 R. P. M.

A still further modification involving the use of a pair of matchedprimary coils 2 9, 3.! wired in circuit with a battery 26, isillustrated in Figme 10 and in which the plurality of contact points .2are arranged in twoassemblies and adapted to be operated by two multilobe cams 3a and. in which the lobes are out of registry as aforesaid.

In the last mentioned embodimentythe magneto is assumed to include afour pole rotor. A four segment commutator and two four lobe cams arealso employed The cams are operatively connected with the rotorand'commutatorshafts in such a manner that the speed of the rotor andcommutator brush is four times that of the cam shaft-- This system iscapable of providing efficient ignition to a forty-two cylinder fourstroke internal combustion engine operating at 3,000 R. P. M. whichnecessitates the provision of 63,000 impulses per minute at a magnetorotor speed of 15,750 R. P. M; Due to this relatively high rotor speedthe magneto may be driven directly by gearing or in any other suitablemanner by the cam ring of a radial engine. In addition the weight of themagneto may be reduced to a minimum. The approximate maximum capacity ofan ignition system in accordance with the last mentioned embodimentwould be approximately 00,000 impulses per minute at a rotor speed of25,000 R. P. M.

It will also be readily apparent that the embodiments illustrated inFigures 8, 9 and 10 not only provide a materially increased output asaforesaid but also are adapted to furnish an eiiicient supply of currentfor starting as well as throughout the whole of the engine speed rangewithout having to cut off the supply of supplementary battery current.

In order to meet the requirements of dual ignition, a common rotor maybe employed to flux two adjacent induction coil cores in any suitablemanner and a common commutator may be operatively connected to twoseries of reciprocatory contacts functioning as breaker points asaforesaid.

Various alterations, modifications and/or additions may be introducedinto the foregoin construction and arrangement of parts withoutdeparting from the ambit of the invention as defined by the appendedclaims.

Having now described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. An improved ignition system for internal combustion and like enginescomprising a magneto fitted with an induction coil having a primarywinding common to a plurality of circuits, a plurality of cam operableand independent pairs of relatively. reciprocatory contacts included inat least one of said circuits, rotatable circuit maker means which arealso common to said circuits and are capable of being electricallyconnected in series with any one of said pairs of contacts forsuccessively including not more than one at a time of said pairs ofcontacts in circuit with the primary winding, said cam being rotatableand operatively connected to said rotatable circuit maker means so thattheir speeds are synchronised whereby a greater output of electricalimpulses is obtainable than would be possible if the ignition systemincluded a single pair of contacts only for making and breaking theprimary circuit and without reducing the minimum time required'forensuring efiective closing of each of said plurality of contacts.

2. An ignition system according to claim 1 wherein said contact selectormeans consists of a commutator the segments of which correspond innumber with the magnetic poles of the magneto rotor and are eachelectrically connected through at least one of said pairs of contactswith one end of said primary winding, the other end of which iselectrically connected to the brush of said commutator, said brush andthe magneto rotor shaft being operatively connected together so as torotate at the same speed.

3. An improved ignition system for internal combustion and like enginescomprising an induction coil having a primary .winding which is commonto a plurality of circuits, a plurality of pairs of circuit breakercontacts which are relatively reciprocatory and mechanically operable,each pair of contacts being included in at least one of said circuits,separate circuit maker means which are also common to said circuits forcompleting each of them in sequence to the exclusion of all others, andmeans for synchronizing the movements of said pairs of circuit breakercontacts and said circuit maker means whereby a greater output ofelectrical impulses is obtainable than would be possible if the ignitionsystem included a single pair of contacts only for both making andbreaking the primary circuit.

l. An ignition system according to claim 3 wherein said contact selectormeans consists of a commutator the segments of which correspond innumber with the number of said pairs of contacts, each segment beingelectrically connected to a contact of one of said pairs of contactswhich are adapted to be actuated by a cam operable at the same speed asthe brush of said commutator.

5. An ignition system according to claim 3 wherein said contact selectormeans consists of a commutator the segments of which are greater innumber than the number of said pairs of contacts each of which iselectrically connected to two or more segments, said pairs of contactsbeing adapted to be actuated by a cam which is operatively connected tosaid commutator in such a manner that the commutator brush speed isgreater than that of said cam.

6. An ignition system according to claim 3 wherein said pairs ofcontacts are arranged in two or more assemblies each of which isoperable by a separate cam, the lobes of said cams being out ofregistry.

7. An ignition system according to claim 3 wherein said means forenergising said primary winding includes a magneto, said contactselector means consists of a commutator and a rotatable cam is providedfor actuating said plurality of contacts, the brush of said commutatorand said cam being operatively positioned in longitudinally spacedrelationship on the rotor shaft of said magneto. I

8. An ignition system according to claim 3 wherein said means forenergising said primary winding includes a magneto, said contactselector means consists of a commutator and a rotatable, cam is providedfor actuating said plurality of contacts, the brush of said commutatorbeing mounted upon the magneto rotor shaft whilst said cam is carried bya separate shaft which is geared or otherwise operatively connected withsaid rotor shaft so that the speeds of said commutator brush and cam maybe synchronised.

9. An ignition system according to claim 3 wherein said means forenergising said primary winding includes a magneto, said contactselector means consists of a commutator and a rotatable cam or cams isor are provided for actuating said plurality of contacts, saidcommutator the plurality of pairs of contacts and the rotatable cam orcams associated therewith being mounted in acasing separate from saidmagneto to the pri mary winding of whichthe commutator segments and theplurality of contacts are electrically connected.

10. An ignition system'according to claims,

wherein both a magneto and a battery are provided for energising saidprimary winding which consists of at least two sections, said contactselector means being also adapted to perform the additional function ofalternately including said sections in the battery circuit in such amanner me h battery r nt flewsfirs n. ne c ca-:-

tion in one of said sections and thence in the opposite direction in theother section to thereby alternately reverse the battery current flux insaid induction coil, the movements of said contact selector means andsaid pairs of contacts being synchronised with the movements of themagneto shaft to thereby substantially match the reversing batterycurrent flux in said induction coil with the alternating magneto fluxtherein thus providing efiicient ignition for engine starting as well asthrough the restof the engine speed range without having to cut off thebattery current.

11. An ignition system according to claim 3 wherein both a magneto and abattery are provided for energising said primary winding which consistsof two separate and substantially identical coils wound inlongitudinally spaced relationship upon a common core so as to ensuresubstantial matching of said coils and minimise undesirable interferencetherebetween, said contact selector means being also adapted to performthe additional function of alternately including said said sections inthe battery circuit in such a manner that the battery current flowsfirst in one direction in one of said sections and thence in theopposite direction in the other section to thereby alternately reversethe battery current flux in said induction coil, the movements of saidcontact selector means and said pairs of contacts being synchronisedwith the movements of the magneto shaft to thereby substantially matchthe reversing battery current flux in said induction coil with thealternating magneto flux therein thus providing efiicient ignition forengine starting as well as through the rest of the engine speed rangewithout having to cut off the battery current.

12. An ignition system according to claim 3 wherein both a magneto and abattery are provided for energising said primary winding which consistsof a single coil provided with a substantially central tap connected toa common lead from said battery circuit so as to electrically divide theprimary winding into said sections, said contact selector means beingalso adapted to perform the additional function of alternately includingsaid sections in the battery circuit in such a manner that the batterycurrent fiows first in one direction in one of said sections and thencein the opposite direction in the other section to thereby alternatelyreverse the battery current flux in said induction coil, the movementsof said contact selector means and said pairs of contacts beingsynchronised with the movements of the magneto shaft to therebysubstantially match the reversing battery current flux in said inductioncoil with the alternating magneto flux therein thus providing efficientignition for engine starting as well as through the rest of the enginespeed range without having to cut off the battery current.

13. For use in an ignition system according to claim 3 a magnetoincorporating a plurality of pairs of relatively reciprocatory contactscapable of being wired in circuit with the primary winding of theinduction coil of said magneto, a rotatable cam for actuating saidcontacts and a commutator forming rotatable contact selector means, thebrush of said commutator and said cam being operatively connected withthe magneto rotor shaft so that their speeds may be synchronised.

ERIC GLEN MACKAY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 685,960 Wirt Nov. 5, 1901 915,389Varley Mar. 16-, 1909 960,598 Springer June 7, 1910 2,089,696 Gough etal Aug. 10, 1937 2,197,114 Rabezzana et al. Apr. 16, 1940 2,215,106Lefebvre Sept. 17, 1940 2,217,232 Nowosielski Oct. 8, 1940 2,377,353Messerschmidt June 5, 1945

